Process of making ketene



Patented Aug. 6, 1929.

UNITED STATES 1,723,724 PATENT OFFICE.

HANS T. CLARKE AND CHARLES E. WAIEING, OF ROCHESTER, NEW YORK, ASSIGNORS TO EASTMAN KODAK COMPANY, OF ROCHESTER, NEW YORK, A CORPORATION OF NEW YORK.

PROCESS OF MAKING KETENE.

No Drawing.

' This invention relates to processes for the manufacture of ketene. One object of the invention is to provide a process in which compounds convertible into ketene may be so converted without undue decomposition.

Another object of the invention is to provide a process in which the heat is efiiciently and economically transferred to the vapors to be converted. A further object is to insure that all particles of the vapor reach the required decomposition temperature. Still another object is to maintain the said vapors of the compound, to be decomposed into ketene, at a specified temperature for the optimum reaction period. Other objects will hereinafter appear.

It was shown in 1910 by Schmidlin and Bergmann (Berichte der Deutschen Chemischen Gesellschaft, vol. 43, p. 2821) that acetone vapor, when passed through a combustion tube, reacted to form ketene. Hurd and Cochran, J. Amer. Chem. Soc. 45, page 515, 1923, repeated the work of Schmidlin and Bergmann, using a combustion tube filled with brocken porcelain and obtained, at a temperature of 600 C., slightly less than 11% of available ketene. These and other investigators believed that a much larger amount of ketene had been initially formed and subsequently decomposed, as they found the resulting decomposition products, ethylene and carbon monoxide in considerable quantities.

D. A. Nightingale in U. S. Patent No. 1,602,699, describes the use of a preventive catalyst, which counteracts the degenerative decomposition, noted above. He was enabled by the use of this cataylst and a temperature of between 600 C. and 675 C. to obtain a yield of more than 80% of the theoretical amount of ketene,-while without his catalyst less than 20% was produced.

From the prior work it would, therefore, be supposed that the essential procedure to be followed in order to realize a high yield in manufacturing ketene comprises accurate temperature control, and the use of some preventive catalyst. We have found, on the other hand, that the catalyst is not necessary. The precautionary measures of excluding mote the egenerative decomposition, and also of insuring the optimum time, of contactat the correct operating temperature will resalt in an equally high yield.

Application filed April 13,

from the apparatus certain metals that prov 1928. Serial No. 269,863.

In our investigation of this subject, it was determined that certain metals apparently catalyze an entirely different reaction in which carbon is deposited in large quantities and the yield of ketene is enormously dccreased if not completely inhibited. Certain metals, such as iron or nickel, or their salts. if present even in minute quantities, cause a very marked reduction in the yield.

The previous work on the manufacture of ketene has been carried out on a laboratory scale in which combustion tubes of small diameter have been used. In working on a semi-production basis employing larger tubes we found that the percentage of c'onversion was considerably decreased with a large quantity of the starting material appearing in the final product unchanged. \Ve were then using, as a filling material for the combustion tubes, an inert material which had been leached with nitric and hydrochloric acids to remove all traces of the decomposing catalysts. It was evident that all points within the combustion tube were not at the correct reaction temperature, the center, naturally, being cooler than the wall. 'VVc found that by packing the combustion tube with fragments or turnings of a good heat conductor, such as copper, we were able to bring the efficiency to a much higher value.

The effect of using copper as a filling material does not increase the percentage yield but, because of its excellent heat conductivity, raises the temperature of the vapors quickly to the reaction temperature. This prevents undue degenerative decomposition of the ketene which results when the kctene is retained at the operating heat for any appreciable time. i

The number of metals. that can replace copper are necessarily limited. They should have a higher melting point than the operating temperature used and should be free from iron or other metals that promote the breaking down of the ketene. Metals other than iron and nickel having a melting point. above 700 C. and a coeflicient of heat conductivity of more than .150 C. G. S. system, may be used. We have found that copper, its alloys,

brass, bronze, and the like, and silver, work entirely satisfactorily.

The time of contact of the starting material at the operating temperature is offirst importance,over-exposure at this temperature will greatly decrease the useful yield and under-exposure will permit an unnecessarily large proportion of the star-ting material to pass through the combustion chamber unchanged, the optimum time of contact for acetone vapor in the heated zone being not more than five seconds.

We shall now describe our invention by way of example, but it will be understood that the invention is not limited to the details thus given, except as indicated in the appended claims.

Acetone is vaporized by boiling at a predetermined rate, and the vapor is passed into the copper reaction tube having a diameter of the order of a half inch or more, filled with copper turnings, and heated to 650670 C. The acetone vapor is conducted into the reaction chamber at such a rate that the acetone is at the optimum temperature, during a period of time less than five seconds. The unchanged acetone is condensed and returned to the boiling vessel, and the gaseous reaction products are condensed or absorbed in any desired manner. After about eight hours operation a yield of approximately 80% is realized.

It is to be understood that while we have described the use of metal filings or turnings as our preferred filler, other forms may be used giving an equivalent cellular effect, that is, providing a considerable area of unimpeded air space with comparatively thin walls or masses of heat conductive material in a sponge or network throughout the space.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent is:

1. The method of manufacturing ketene which comprises passing the vapors of organic compounds which are decomposed by ieat into substances including ketene through a chamber having therein a network of metal which is free from iron and nickel, said metal having high thermal conductivity and a melting point above the reaction temperature.

2. The method of manufacturing ketene which comprises passing the Vapors of organic compounds which are decomposed by heat into substances including ketene through a chamber having therein a network of metal which is free from iron and nickel, said metal having a melting point above 700 C. and a coefiicient of heat conductivity greater than .150, C. G. S. units.

3. The method of manufacturing ketene which comprises passing the vapors of acetone through a chamber having therein a network of metal which is free from iron and nickel, said metal having a melting point above 700 C. and a cocflicient of heat conductivity greater than .150 C. G. units.

4. The method of manufacturing ketene which comprises passing the vapors of organic compounds which are decomposed by heat into substances including ketene through a chamber having therein a network of metal which is free from iron and nickel, said metal having a melting point above 700 C. and a coefficient of heat conductivity greater than .150 C. G. S. units, maintaining said chamber at a temperature of 650-670? (1., the period of contact of the vapor with the network being less than five seconds.

5. The process of manufacturing ketene which comprises passing the vapors of acctone through a chamber containing a network of copper, said chamber and copper being free from iron and nickel.

6. The PlOCeiS of manufacturing ketene which comprises passing the vapors of acetone through a chamber containing a network of copper, at a temperature of 650-670 (1, said chamber and network bein free of nickel and iron.

7. The process of manufacturing ketene which comprises passing the vapors of acetone through a chamber containing a network of copper, at a temperature of 650-670 0., said chamber and network being free of nickel and iron, the period of contact between the vapors and network being less than five seconds.

8. The process of manufacturing ketene which comprises passing the vapors of acetone through a copper chamber containing a network of copper, said chamber and network being free of nickel and iron, at a temperature of 650670 C., the period of said passage being less than five seconds.

Signed at Rochester, New York, this 9 day of April, 1928.

HANS T. CLARKE. CHARLES E. VVARING. 

